evaluating the potential risk of dusts generated from
TRANSCRIPT
Chongyang (Oliver) Li and Sanjai J. Parikh
Department of Land, Air and Water Resources, UC Davis
June 6 2018
Evaluating the potential risk of dusts generated from biochar-amended
agricultural soils under simulated tillage
Tillage (Mechanical disturbance)Natural wind erosion
(Fugitive dust)
VS.
High potential for dust generation from agricultural fields!
Biosolid
Manure
Compost
Fertilizer
Biochar
Mauri et al., 2016
• Biochars can have low bulk densities
• Biochars are often very porous and have high surface areas
Byrne and Nagle, 1997
Rombolà et al., 2016
Sigmund et al., 2017
• Biochar particles may lower the cell viability
• Carcinogenic or endocrine-disrupting suspects may be
generated during the biochar production procedure
Research Questions
1: More dust produced?Non amended soils Biochar amended soils
2: Dust containing more toxic compounds?
Field Sampling
Laboratory Simulation
Domingo and Southard, 2006
Southard et al., 2006
Lab approach selected…..
• Minimize logistical challenges:-Weather conditions-Agronomic practices-Tillage operation
conditions
• A controlled approach is better for comparing effects from selected variables
Field Sampling vs Laboratory Simulations
Soils
Biochars
Ponderosa pine wood or PW at 500, 700 and 900 ˚C
Silt Loam (SiL) Sandy Loam (SL)
Walnut shell or WS at 900 ˚C
Materials
Optimized Operation Conditions:
Soil Mass: 300g;
Rotation Rate: 16 rpm;
Blower: ¼ open;
Sampling Time: 3 min;
Vacuum pump flow rate: 4L/min.
Madden et al., 2010
PM10
or
PM100
Dust collection
BC marker method: BPCA
+ 65% HNO3 at 170˚C for 8 hours
Biochar content determination
Detected on liquid chromatography
CALUX Bioassay
Denison et al., 2004
If any aryl hydrocarbons (dioxins, poly aromatic hydrocarbons, etc.) are present, the cell fluoresces.
Evaluating impact of biochar type (constant application rate)
Airborne particle concentration Biochar content in dust
Li et al. Sci. Total Environ. 2018
Walnut shell biochar (WS900) at varied application rate
Airborne particle concentration Biochar content in dust
Li et al. Sci. Total Environ. 2018
Why does WS 900 biochar result in more dust emissions?
WS 900 biochar contains a considerable amount of potassium (>5% by mass)
Potassium ions disperse aggregates and form finer particles
Airborne particle concentration Biochar content in dust
Permanent wilting point
Field capacity
Walnut shell biochar (WS900) at varied moisture levels
Li et al. Sci. Total Environ. 2018
Bioassays to probe potential toxicity
Using different biochars Using WS 900 with different dose
Li et al. Sci. In prep.
Impact of biochar type Impact of application rate (WS900)
Bioassays to probe potential toxicity
Different feedstock have different chemical composition
Need further exploration
Char with more dioxin-like compounds
Char with less dioxin-like compounds
Production procedures are different:O2 contents?Metal catalyzation?
What might be there in WS 900 and what are the possible causes?
• Not all biochars are problematic for dust emissions (e.g. PW biochars).
• To reduce dust, biochar can be incorporated in bands directly above the drip tape at low and high rates, and buried;
• Apply only when wind levels are low and with water added to biochar if possible;
• Appropriate personal protection equipment is required, this include respirators that are verified to fit the user;
• Test biochars in advance
• WS 900 biochar amended soils emitted more dusts than soil alone, and with higher contents of dioxin-like compounds in dusts;
Summary
AcknowledgementsFunding:•Western Center for Agricultural Health and Safety Grant
•Henry A. Jastro Graduate Research Award
•USDA National Institute of Food and Agriculture (NIFA) for Hatch Formula Funding
Technical support:• Randal Southard for access to
the dust generator and Peter Narby for instructions on its usage
• Dr. Bryan Jenkins and Adina Boyce (UC Davis Biomass Laboratory) for producing and providing pine wood biochars